1. Field of the Invention
The present invention relates to a driving device for rotatable cassette to be used for feeding copy material longitudinally or laterally at will, such as for example a driving device used in copying machines, laser printers, over-head projectors and other apparatuses. To be precise, the present invention relates to a feeding device comprising a supporting device for supporting a pivotal copy material holding plate used for raising the copy material stored in the rotatable cassette.
2. Description of Related Art
In the conventional art, for example in a copying machine, there is installed a paper feeding device that supplies copy paper to the main body of the copying machine, and that is provided with a plurality of paper feeding cassettes for each copy paper size. For conveying the copy paper from the paper feeding device, lateral feed where the transport direction coincides with the crosswise direction of the copy paper, is preferred in terms of transport time to longitudinal feed where the transport direction coincides with the lengthwise direction of the copy paper. Some copying machines even laterally feed copy paper sheets of B4 and A3 sizes.
However, feeding large size copy paper laterally causes the photosensitive drum, the transport rollers, the transport path of the paper, and other parts inside the copying machine to become large. As a result the copying machine itself becomes large and bulky, and its cost rises. Hence generally, the method of longitudinally feeding copy paper of a large size such as A3 or B4, and laterally feeding copy paper of a size not larger than A4, is adopted.
However, with such an arrangement, in a copying machine provided with a variable magnification function that performs reductions and enlargements, for instance B5R and A4R paper feeding cassettes that feed the copy paper longitudinally, are necessary to perform reduced copies. In addition, when thinking of transport time, A4 and B5 paper feeding cassettes that feed the copy paper laterally, are also necessary. Accordingly, when it comes to installing those different types of paper feeding cassettes, either the paper feeding device has to be designed in a large size, or the paper feeding cassettes must be changed as occasion calls. This causes the size of the copying machine to be large and its cost to rise, or the operation of the copying machine to become complicated.
Hence, in order to avoid such a problem, an arrangement is suggested as disclosed in Japanese Publication for Unexamined Patent Application No. 59245/1981 and No. 59251/1981, (Tokukaisho No. 56-59245 and Tokukaisho No. 56-59251). Namely, a common paper feeding cassette is used both as B5 paper feeding cassette and B5R paper feeding cassette, and a common paper feeding cassette is used both as A4 paper feeding cassette and A4R paper feeding cassette. The copy paper is fed laterally or longitudinally by changing the feed position of the copy paper stored in the paper feeding cassettes.
However, with the above conventional arrangement, when the feed position of the copy paper stored in the paper feeding cassette is changed, the distance separating the paper feeding cassette and a pick-up roller differs when the copy paper is placed in the lateral feed position and when the copy paper is placed in the longitudinal feed position. Consequently, after the feed position of the copy paper stored in the paper feeding cassette is shifted to the lateral feed position, either the paper feeding cassette has to be brought close to the pick-up roller, or the pick-up roller has to be brought close to the paper feeding cassette. This means that in addition to the device for changing the feed position of the copy paper, a motion device for moving the paper feeding cassette or the pick-up roller needs to be installed, thereby causing the structure to become complex and expensive. Moreover as it takes time for the motion device to move the paper feeding cassette or the pick-up roller, the copy paper cannot be fed rapidly. Specially, when the motion device is arranged such that the pick-up roller is moved, the transport path of the copy paper gets longer as the leading edge of the copy paper placed in the lateral feed position recedes as compared to when the copy paper is placed in the longitudinal feed position. Therefore, the advantages that were obtained by changing the feed position of the copy paper stored in the paper feeding cassette are reduced by half.
Moreover, with the conventional arrangement, in order to forward the copy paper stacked in the paper feeding cassette by means of the pick-up roller, the topmost copy paper sheet needs to be raised to a position where it can be in contact with the pick-up roller. As means that responds to this requirement, there is known the device of the above publication, as well as, adapted not to a rotatable cassette but to a fixed cassette, for example a device as disclosed in Japanese Publication for Examined Patent Application No. 58374/1986 (Tokukosho No. 61-58374).
When in order to lift the copy paper, a pivotal paper holding plate whereon the copy paper is stacked pivots in the vertical direction, the angle by which the pivotal paper holding plate is lifted increases as the amount of remaining copy paper decreases. As the angle by which the pivotal paper holding plate is lifted increases, the forwarding direction of the copy paper stacked on the pivotal paper holding plate is shifted with respect to a feeding mechanism constituted by the pick-up roller and other members. The above publication discloses a device in which in a fixed cassette, with an inclined part declining forwards, is accommodated in the paper feeding section of the pivotal paper holding plate. However, such an inclined Part is not provided in a pivotal paper holding plate of the rotatable cassette and as mentioned earlier the forwarding direction of the copy paper stacked on the pivotal paper holding plate is shifted with respect to the feeding mechanism.
In order to forward the copy paper stacked in the paper feeding cassette with the pick-up roller, the topmost copy paper sheet needs to lifted to a position where it can be in contact with the pick-up roller. As means to respond to this requirement, in addition to the device disclosed in the above publication there is also known a device as disclosed in Japanese Publication for Unexamined Utility Model Application No. 192836/1983 (Jitsukaisho No. 58-192836). The supporting structure involved is constituted by a pivotal paper holding plate whereon copy paper is stacked, that is merely placed inside a paper feeding cassette. The pivotal paper holding plate has a longitudinal paper feeding section and a lateral paper feeding section. When lifting each paper feeding section of the pivotal paper holding plate, use has been made of the fact that each non-feeding section naturally forms the fulcrum about which the pivotal paper holding plate pivots, and the lateral wall of the paper feeding cassette serves as a guide during the pivoting process.
However, with the structure described above, a shift in the position of the pivotal paper holding plate (shift in the horizontal direction) is likely to occur. For instance, when the copy paper is shifted with respect to the paper feed direction, the position of the leading edge of the copy paper is shifted thereby causing the distance between the copy paper and the pick-up roller to be disparate. Besides, a shift of the copy paper with respect to the direction orthogonal to the paper feed direction causes the center of the copy paper to be shifted. Furthermore, when the pivotal paper holding plate is moved in the horizontal plane, the copy paper is sent slantwise which might cause a hindrance to the paper feeding process.